To solve this problem, we need to understand how electrons are distinguished in the same orbital.$\\$Electrons in an atom are described by four quantum numbers:$\\$• Principal quantum number $(n)$ which indicates the energy level.$\\$• Azimuthal quantum number $(l)$ which indicates the shape of the orbital.$\\$• Magnetic quantum number $(m_l)$ which indicates the orientation of the orbital.$\\$• Spin quantum number $(m_s)$ which indicates the spin of the electron.$\\$In the same orbital, the first three quantum numbers $(n, l, m_l)$ are identical for both electrons.$\\$However, the spin quantum number $(m_s)$ can have two possible values: $+\frac{1}{2}$ or $-\frac{1}{2}. \\$These two values of $m_s$ allow two electrons to occupy the same orbital with opposite spins.$\\$Thus, two electrons in the same orbital are distinguished by their spin quantum number.$\\$Therefore, the correct option is Option 4: Spin quantum number.